Sulphurized oils



Patented Apr. 12, 1938 I 2,1 ,8 l

UNITED STATES PATENT OFFICE SULPHURIZED OILS Bert H. Lincoln and Waldo L. Steiner, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware No Drawing. Application December 28, 1936,

Serial No. 117,900

Claims. (Cl. 87-9) Our invention relates to sulphurized oils and erties with respect to the new type of soft more particularly to lubricants containing a spemetal bearings. cific class of sulphur containing compounds. 'I'his- Another object of our invention is to provide pp i i n is a ontinuation in p rt f o r a lubricant containing a small amount of a sul- 5 copending application, Serial No. 11,588, filed phurized monohydric or dihydric ester which 5 March 18,1935. lubricant will not be corrosive to bearings-0f I 011 S d c pe di g application, we have disthe soft metal group, but which will, nevertheclosed an improved type of suphurized oil preless, be sufiiciently chemically active to precipitate pared by adding to a hydrocarbon oil a dihydric objectionable compounds of such metals as sulor monohydric ester of an unsaturated organic phides. l0 acid, which ester has been sulphurized. In said Another object of our invention is to provide application, the value of a sulphurized oil made a lubricant possessing a high degree of oiliness. in accordance with our application for use in Another object of our invention is to'provide cutting lubricants, extreme pressure lubricants a lubricant which will possess a decreased rate 01' and crank case lubricants was pointed out. Suloxidation. 15 phurized oils, made by adding sulphurized glyc- Another object of our invention is to provide a erides or sulphurized vegetable or animal oils lubricant of minimized sludging characteristics. to lubricants, have long been known but these Other and further objects of our inventionoils do not possess the advantages of oils comwill appear from the following description. pounded by the use of sulphurized dihydric and We have pointed out in our copending applicamonohydric esters. The advantage of oils comtion, Serial No. 11,588 that the monohydric and pounded with monohydric or dihydric esters dihydric esters of unsaturated fatty acids, when arises from the fact that no derivatives of glycsulphurized, will yield products which may be erine are present, which derivatives will break added to a hydrocarbon oil to. obtain an imdown, liberating glycerine which is easily polyproved lubricant. 5 merized or oxidized. The presence of glycerine, We have discovered that certain of the monotherefore, will cause gumming and sludging, hydric and dihydric esters, when prepared in a which is deleterious, especially'in case of internal certain manner, are superior corrosion inhibitors combustion engines where high temperatures and and are therefore especially desirable -for use 7 pressures are involved, which will readily facilwith the new type soft metal bearings. Certain itate gumming and sludging. of these compounds falling within the generic Lubricating oils prepared with monohydric and class and prepared in accordance with our invendihydric esters have the further advantage of tion have the further advantage that they are being less viscous than those prepared by suloxidation and sludging inhibitors.

phurized glycerides. Moreover the viscosity does We do not know the theory of the new eifects 35 not increase as rapidly on long time heating with produced. We believe, however, that the corrosulphurized monohydric and dihydric ester. This sion inhibiting and anti-oxidation effects of these is very important in commercial lubricants. monohydric and dihydric esters, prepared in a Higher speeds and greater bearing pressures certain manner, may be explained. Most metals 0 in modern internal combustion engines have tend to act as catalysts, increasing the rate of 40 made it necessary for automotive engineers to oxidation. For example, when a hydrocarbon oil develop. improved bearings. Modern bearings is heated in contact with air in the presence of which have resulted from this improvement are copper, a sludge comprising hydrocarbon oxidaof three general types, namely those compristion products will form much more rapidly than mg generally cadmium alloys, those comprisif the oil is heated to the same temperature in a 45 ing generally mixtures of copper and lead toglass container, out of contact with copper. This gether with small amounts of other metals, and oxidation increasing effect of metals is true to alloys containing a high percentage of lead. various degrees for other metals. Soaps and While these new bearing materials are capable oxides of suchmetals as calcium, cadmium and of withstanding higher pressures and greater iron are catalysts in oxidation reactions for 50 speeds than the old Babbitt bearings, they are petroleum derivatives and are used, for example, more susceptible to corrosion, resulting from the in the preparation of fatty acids and other oxidaaction of oxidation products of the lubricants. tion products from hydrocarbons. sulphurized One object of our invention is to provide a esters of our invention are strongly polar comsulphurized lubricant of inhibited corrosion proppounds and we believe they tend to form a pro- 55 metal.

tective layer over metallic parts, serving to insulate the metal from the main body of oil, thus inhibiting the oxidation catalytic effect of the We believe, further, that traces of such metallic salts as do form, such as iron soaps, copper soaps, and cadmium soaps, which result from the reaction of the oxidized hydrocarbons with the metals are precipitated by the sulphur in our sulphuretted esters. The sulphides are insoluble in hydrocarbon oil and are much poorer oxidation catalysts than the soaps and the metals themselves. By the formation of sulphides and their precipitation, the catalytic effect is decreased and the oxidation is minimized.

We have discovered that certain types of sulphurized esters are superior to others and that these could be most advantageously prepared in certain ways. This type consists of monohydric and dihydric esters, prepared from fatty oils in which the linoleic or similar two double-bonded fatty acid content ranges from 10 to 60 per cent and in which the linolenic or similar three or more double-bonded fatty acid is present in quantities less than 5 per cent. Examples of fatty oils in which the fatty acid content meets these requirements are as follows:

Per cent ig a g linolenic or two or three double or more bonded doubleacid bonded acid Percent Percent Rape seed oil 15 l Arachis oil. 21 Cottonseed o'l 53. 0 0 Maize oil 41. 6 O Ravison oil. 27 2 Sunflower seed oil 58. 4 0 Soya bean oil 57. 5 2. 2

Linseed oil, for example, would not meet the requirements, since its two doublebonded acid content is 62 per cent and its three or more doublebonded acid content is 24 per cent. Menhaden oil would not be available, .since its per cent linoleic or two is 29.6 per cent, while its linolenic or three or more doublebonded acid content is 31 per cent.

The fatty oils of high unsaturation, as represented by linseed oil, menhaden oil, whale oil, and sperm oil, are unsatisfactory. These highly unsaturated oils form insoluble products upon being sulphurized. Then, too, they form tarry and gummy products when employed as lubricants. If the unsaturation, however, is reduced by hydrogenating or partially hydrogenating them to reduce the three or more doublebonded acid content but leaving a substantial percentage of linoleic or two doublebonded acid content, then they may be satisfactorily used in our invention. The fatty oils or fatty acids of the single doublebond type such as oleic or erucic acids, yield sulphurized esters which are only partially satisfactory as oxidation and corrosion inhibitors. We attribute this to the fact that they do not take up as much sulphur as fatty oils and fatty acids having a high percentage of two doublebonded or linoleic acid in which the sulphur which is taken up is more firmly held. The result is that, if sulphurized esters are made from single doublebonded fatty acids a larger amount of inhibitor is required to stop corrosion, which results in a dark color for the blended lubricant. This darkcolor is objectionable from a sales standpoint and, furthermore, the emdoublebonded acid content.

ployment of a greater amount of inhibitor is expensive.

In preparing our inhibitors, fatty oils of the type described are applicable to our invention, that is, those having a high acid content of the two doublebonded acid type while having a small linolenic acid content. The oils are first converted into the corresponding dihydric or monohydric ester in any suitable manner, for example, the oil may be refluxed with an equal volume of the desired monohydric or dihydric alcohol containing three per cent of dry hydrochloric acid for several hours. On cooling the alcohol glycerol layer is separated and the refluxing operation repeated. This procedure converts all of the original glycerides into the desired alcohol ester and, at the same time, eliminates most of the unsaponifiable matter in the whole oil. The ester is then water washed and dried. The esters, of course may be made by directly esterifying the fatty acids. The esters alone or admixed with petroleum oil are heated to a, temperature between 360 and 390 F., and from 5' per cent to 20 per cent or more of elemental sulphur is slowly stirred in until it is combined. When higher percentages of sulphur are used, the temperature must be raised from 410 to 420 F. for a short period after the sulphur has apparently dissolved or combined. Sometimes-it is desirable to continue this higher temperature range for a period of about an hour. While adding the sulphur, care must be exercised to prevent the heat of reaction from raising the temperature appreciably above 400 F. This can be done by controlling the heatlng step, it being remembered that the sulphur combining reaction is an exothermic one. Temperatures outside the range of 360 to 390 F. may be used but we find the results are not as good as when the temperature range mentioned is employed. Higher or lower temperatures may be employed by varying the time of heating. The sulphurized esters may be refined to improve their color, by treatment with activated clay or carbon or by using fullers earth, silica gel, bentonite, and other decolorizing methods.

Inhibitors thus prepared may be added to hydrocarbon oils in amounts from .01 per cent to 5 per cent by weight. Amounts in excess of 5 per cent may be added without injury, but it does not appear that any further results will be achieved by adding greater amounts.

A machine for testing corrosiveness of lubricating oils on soft metal bearings employed by us consists of four connecting rods provided with a four speed lubrication arrangement. The soft metal bearings were employed on the shaft and connecting rod bearings. The crank shaft was turned at a speed of 1,250 R. P. M. The connecting rods lay fiat and the piston ends were free to rub upon an iron plate. Two quarts of oil were used in the lubricating system and the temperature was maintained at 350 F. The test was run for twenty-two hours.

A high grade ordinary hydrocarbon lubricating oil was tested in the machine above described and it was found that, for a cadmium alloy hearing and a copper lead bearing, a loss of over one gram per bearing insert was experienced. The oil contained 14.6 per cent of sludge. The same oil was then blended with two tenths of one per cent of a sulphurized ester of linoleic acid, that is, a sulphurized ester made from an'organic acid, having a high linoleic acid content and a comparatively low linolenic acid content, and containing 15 per cent by weight of sulphur.. This blend was then tested upon the same machine and under the same conditions. It was found that the corrosion per bearing insert on both the cadmium alloy bearing insert and the copper lead bearing insert was about .06 of a gram per bearing insert and the oil contained only 5.2 per cent of sludge.

Another apparatus for measuring the corrosion tendencies of lubricating oils, under conditions approximating use, is the Underwood" machine, which was developed by the General Motors research. department and is described in their literature and is known to those skilled in the art. In this machine, jets of oil under pressure of ten pounds per square inch are directed at half bearing inserts in the presence of air, the 011 being held at a temperature of 325 to 350 F. The test is usually run for about five hours.

A well refined hydrocarbon lubricating oil containing .05 of one per cent of lead oxide in the form of lead naphthenate was tested. The lead naphthenate was employed to speed up the rate of corrosion and thereby shorten the time required for the test. Using this blend without any corrosion inhibitor, there was .570 mg. loss on the copper lead alloy and 1710 mg. on the cadmium alloy. Another portion of the same lubricating oil containing .05 of one per cent of lead oxide in the form of lead naphthenate was then blended with .2 of one per cent of sulphurized methyl esters of corn oil fatty acids containing 15 per cent sulphur. The test on the Underwood apparatus was repeated under exactly the same conditions. It was found that the loss of metal from corrosion for a copper lead bearing alloy was 60 mg. and for a cadmium alloy only 10 mg.

Another blend was made from another portion of the same test oil base, that is, the hydrocarbon oil containing .05 of one per cent of lead oxide in the form of lead napthenate with a sulphurized ester of oleic acid, namely sulphurized methyl oleate containing 20 per cent sulphur. .2 of one per cent of the sulphurized methyl .oleate was used in making the blend. The loss on the copper lead bearing was 500 mg. and the loss on the cadmium alloy was 1590 mg.

It will be observed that the tests, (which are "merely representative of many which were con- 210 F. at 30 minutes.

ducted) clearly show the improved results produced by our sulphurized esters of high linoleic acid content without a correspondingly high linolenic acid content.

In the preparation of our inhibitors, we find that better results are obtained if the amount of sulphur employed approximates two atoms per molecule of fatty acid ester. Theheating period of 410 to 420-F. is continued just long enough to give .1 per cent blend in a lubricating oil which will not appreciably darken a copper strip at An inhibitor prepared in the manner just described, that is with approximately two atoms of sulphur per molecule of fatty acid ester, when tested on the Underwood apparatus, using the same test base oil, that is, a hydrocarbon oilcontaining lead oxide in the form of lead naphthenate, which blend contained .1 of one per cent of a sulphuretted methyl ester of soya bean oil containing 18 per cent of sulphur gave a corrosion loss on the copper lead alloy bearing insert of only 10 mg. and on the cadmium alloy bearing insert of 20 mg.

It will be understood that the amount of inhibitor to be used in making a blend with a hydrocarbon oil depends on a number of factors such as the type of crude oil used in manufacturing the hydrocarbon oil, the manner-and degree of refining and the conditions of use. In general, a range from .01 of one per cent to 5 per cent by weight of sulphurized ester will be sufficient for all practical purposes.

It will be understood that our inhibitors may be applied to other lubricants besides hydrocarbon oils. They may be employed for example in greases which are hydrocarbon oils, thickened with soaps. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim is:

1. A lubricant comprising in combination a major proportion of a hydrocarbon oil and a minor proportion of a sulphurized monohydric or dihydric ester of linoleic acid.

2. A lubricant comprising in combination a major proportion of hydrocarbon oil and a minor proportion of sulphurized monohydric or dihydric ester of organic acids, the glycerides of which are present in natural oils, said organic acids having a high percentage of linoleic acid and low percentages of linolenic acid.

3. A lubricant comprising in combination a hydrocarbon oil and from .01 to 5 per cent of a sulphurized monohydric or dihydric ester obtained by esterifying fatty acids derived from naturally occurring glycerides which contain from 60 to 10 per cent of glycerides of linoleic acid and less than 5 per cent of glycerides of linolenic acid with a monohydric or dihydric alcohol.

4. A lubricant comprising in combination a. major proportion of a hydrocarbon oil and a minor proportion of a sulphurized, monohydric or dihydric ester of linoleic acid the glyceride of which is present in oils selected from the following group: rape seed oil, arachis oil, cottonseed oil, maize oil, ravison oil, sunflower seed oil, soya bean oil.

5. A lubricant comprising in combination a major proportion of a hydrocarbon oil and a minor proportion of a sulphurized, monohydric or dihydric ester of linoleic acid the glyceride of which is present in oils selected from the following group: rape seed oil, arachis oil, cottonseed oil, maize oil, ravison oil, sunflower seed oil, soya bean oil, said sulphurized esters containing from 5 per cent to 20 per cent by weight of elemental sulphur.

BERT H. LINCOLN. WALDO L. STEINER. 

